OFFSET
1,3
COMMENTS
Column 2 of A252876.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/24)*n^4 + (5/12)*n^3 - (13/24)*n^2 - (11/12)*n + 1.
Empirical: G.f.: -x^2*(1+3*x-4*x^2+x^3) / (x-1)^5. - R. J. Mathar, Nov 21 2015
EXAMPLE
All solutions for n=3:
..0..0....0..0....0..0....0..1....0..1....0..0....0..1....0..0
..0..0....0..0....0..1....1..1....0..1....0..1....0..1....1..1
..0..1....1..1....1..1....1..1....1..1....0..1....0..1....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 24 2014
STATUS
approved